[joelanman]

(I worked on this pattern) Our guidance is to accept both names and numbers in the back end so people can enter either. In our testing, text inputs (with a numeric keyboard on mobile) is better than selects. Some people struggle with using selects, we don't see those issues in text inputs. That guidance maybe be about people not knowing the order of the inputs (DD MM YY, MM DD YY) but our pattern is clearly labeled for each input so we don't get that issue.

We did continue our testing which resulted in the pattern in the design system which is linked.

[hunter2_]

I'm not sure of every type of trouble folks might have using selects, but for the subset where using a hardware keyboard is required, you can usually type into a focused select just as you can type into a text input. Getting an Android/iOS on-screen keyboard to do this without a special configuration might not be a thing, I'll admit.

The only tricky part, for me, is deciding whether I should type a state abbreviation or a few letters of the full state name, which in my case differ enough to be quite annoying.